1. Field of the Invention
The present invention relates generally to a vehicular lamp for use in a vehicle.
2. Description of the Related Art
Conventionally, a lamp such as a taillight and a stop lamp, is used in a vehicle such as an automobile. In the lamp are provided a light source connected in series with a power supply, and a resistor, connected in series between the light source and power supply, for defining a current to be supplied to the light source. Moreover, a plurality of light sources may be provided in parallel in order to emit light having sufficient light amount. In this case, for each light source, a resistor for defining a current to be supplied to the light source is provided as disclosed, for example, in Japanese Patent Application Laid-Open No. 2001-215913, page 4 and FIG. 8.
In addition, the lamp serves as a plurality of types of lamp that are different in the amount of emitted light, such as the taillight and stop lamp. Thus, resistors having different resistance values are provided for the respective light sources and it is switched which resistor is used for supplying a current to the corresponding light source, thereby switching the amount of the emitted light of the light source as disclosed in Japanese Utility-Model Publication No. 61-48836, page 1, for example.
However, the conventional lamp requires a plurality of resistors for the respective light sources as described above and it is also necessary to provide wirings for connecting the resistors and the power source and the associated light sources, respectively. Thus, the fabrication cost increases. Moreover, in a case where the number of the light sources connected in parallel is increased, it is necessary to increase the resistors and wirings that respectively correspond to the light sources, too. This leads to further increase of the fabrication cost.
In addition, it is necessary to form a lighting circuit for lighting a light source unit in accordance with the number of light sources connected in parallel in the light source unit including a plurality of light sources. That is, when the number of parallel light sources in the light source unit is changed, a different lighting circuit should be used. Thus, the lighting circuit has low versatility.